A fuel cell system is a system configured to generate electric power and heat by an electrochemical reaction between a fuel gas (hydrogen-containing gas) and oxidizing gas (for example, air) supplied to a fuel cell. The electric power generated by a common domestic fuel cell system is supplied to some of home-use electric power loads (for example, electrical appliances, such as lights and air conditioners). The heat generated by the electric power generation is stored as hot water in a hot water tank, and the hot water in the hot water tank is supplied to domestic heat loads (for example, heat utilizing devices, such as water heaters and floor heating).
Since an infrastructure for supplying the hydrogen-containing gas necessary in the electric power generating operation of the fuel cell system is not developed, the fuel cell system is normally provided with a reformer configured to generate the hydrogen-containing gas. The reformer generates the hydrogen-containing gas by causing a steam-reforming reaction in a reforming catalyst between a material gas (gas containing an organic compound (for example, city gas)) and water.
To suppress the deterioration of the reformer and the fuel cell, it is preferable that the water supplied to the reformer be purified water. Here, a fuel cell apparatus is known, in which an activated carbon filter for purifying the water, a reverse osmosis membrane for purifying the water, a water tank for storing the water, an ion-exchange resin for purifying the water, and a water pump for supplying to the reformer the water having flowed through the ion-exchange resin are sequentially connected toward the reformer (see PTL 1). According to the fuel cell apparatus disclosed in PTL 1, tap water or the like flows through the activated carbon filter and the reverse osmosis membrane, and the purified water is stored in the water tank. Then, the water is supplied from the water tank through the purifier including the ion-exchange resin to the reformer in accordance with the amount necessary for the steam-reforming reaction. This can improve water responsiveness (see PTL 1, for example).
A fuel cell electric power generator is known, in which a purifier including an ion-exchange resin is disposed on a water passage through which water supplied from a water tank to a cooling water tank flows (see PTL 2, for example).